1. Field of the Invention
This invention relates to a process for the telomerization of conjugated dienes. More particularly, it relates to a process wherein 1,3-butadiene is alkoxydimerized in the presence of a catalyst containing a noble metal and a triarylphosphine ligand that contains only one ortho-alkoxy group and also contains at least one electron-withdrawing group, which shows desirable stability and selectivity toward the 1-alkoxy octadiene product.
2. Background of the Art
A highly useful chemical for a variety of purposes, 1-octene is produced in various locations throughout the world. It is used, in particular, as a co-monomer in production of polyethylene, and as a starting material to produce linear aldehyde, via an oxo synthesis (hydroformylation), which is in turn used to produce the plasticizer nonanoic acid. The 1-octene may be produced by, for example, the oligomerization of ethylene or by a Fischer-Tropsch synthesis, but an increasingly valuable method is via the telomerization of butadiene. This telomerization reaction involves the oligomerization, and particularly the dimerization, of butadiene with the concomitant addition of a nucleophilic agent. Examples of such agents include compounds containing one or more active hydrogen atoms, such as water, alcohols and amines. The nucleophile is introduced primarily at the terminal position of the oligomer, and especially of the dimer, of the butadiene.
Telomerization reactions catalyzed by Group VIII transition metal catalysts are described extensively in the prior art. Historically, attention was focused primarily on optimization of conversion and selectivity of the telomerization reaction under batch conditions, but eventually focus changed to more easily enable continuous production methods. A focus on catalyst selection led, for economic reasons, to the evolution of processes enabling catalyst reuse. Such often required techniques to separate the catalyst from the product mixture, by means including, for example, distillation, precipitation and/or extraction. Care was required to avoid catalyst decomposition or metallization, which could then require an additional catalyst regeneration step.
Despite the many processes and catalysts that have been identified, such processes continue to produce a variety of products, and selectivity particularly to the product required for production of 1-octene i.e., 1-methoxy-2,7-octadiene (OD-1-R), is generally less than desirable. Accordingly, processes that enhance selectivity to OD-1-R, and that reduce problems such as catalyst instability, continue to be sought.